Synthesis of hybrid spherical silicas and application in catalytic transesterification reaction

- Use of methanol in the synthesis led to the formation of MCM-41.
- Hybrid silicas show catalytic activity toward the transesterification reaction.
- The initial catalysis rates showed higher for the spherical silicas.

There is increasing interest in the use of heterogeneous catalysts for the production of biodiesel. In contrast to homogeneous catalysts, these materials can be readily separated from the reaction system, avoiding contamination of the products and, in principle, they can be reused. These catalysts include the mesoporous hybrid molecular sieves of the M41S family, which offer these advantages when used as catalysts. The aim of the present work was to synthesize these silicas in the form of spheres, and evaluate their activities as heterogeneous catalyst in the transesterification reaction. The hybrid silicas were characterized by small angle X-ray scattering (SAXS), X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen physisorption and thermogravimetry. The results showed that the structure and morphology of the mesoporous silicas containing an organic template could be controlled by varying the alcohol content during the synthesis, leading to the formation of materials with different phases, levels of organization and morphologies. The catalytic activities of the silicas were evaluated using the transesterification reaction of monoalcohols as a model for application in biodiesel production. These spherical hybrid silicas showed a considerable higher initial catalytic rate than the silicas with irregular shape.

418